Spectroscopic measurements on the Andreev reflection probability as a function of temperature

Abstract

The temperature dependence of the Andreev reflection coefficient A(E,T) at a superconductor/normal-metal interface is a key issue for the critical current in a Josephson field-effect transistor at finite temperature. In this letter, we discuss our experimental observations of A(E,T) as a function of temperature determined by point contact spectroscopy. In addition, we point out major discrepancies between our findings and predictions from different theoretical models.